Project Summary The W.M. Keck Center for Cellular Imaging (KCCI) is an internationally recognized center for advanced light microscopy imaging and is particularly known for molecular imaging. The KCCI is a University-wide imaging facility, located within walking distance of all participating investigators from the School of Arts & Sciences, Engineering and Medicine. We are requesting to replace the existing 13- year old discontinued Zeiss 510 confocal/multiphoton microscopy system, purchased through the S10 program, with a high resolution and high-speed Zeiss 880 multiphoton AiryscanFast microscopy system with a QUASAR 32-channel GaAasP high-sensitivity detector and high-speed high-resolution Airyscan detector. We are also requesting to replace the 21-year old manually tunable Coherent Mira 900 system with a digitally tunable Coherent Chameleon Discovery ultrafast 2-photon laser system, which will be coupled to the Zeiss 880 multiphoton AiryscanFast system. The requested instrument will benefit the basic and clinical sciences of this university; in particular, the 11 participating federally funded investigators (major users) and five minor users. The higher quantum efficiency GaAsP detector (45% at 540nm) provides a better option to excite the sample with less excitation intensity and detecting the weaker photons in tissue and intravital imaging. This instrument is essential for our core investigator group and will also be critical for training other investigators and students attending the fall semester microscopy course interested in the study of various biological applications in tissues and live animals. There is currently no Zeiss 880 multiphoton AiryscanFast microscopy system available in the user facility at the University of Virginia that has a digitally tunable laser from 680 to 1300 nm for multiphoton microscopy for intravital or deep tissue imaging, and animals with applications in neuroscience, developmental and cell biology. KCCI is recognized for its annual hands-on training FLIM & FRET workshop, held for the past 17 years at the University of Virginia. The requested Zeiss 880 multiphoton AiryscanFast microscopy is an advanced technology, which will be housed in the Zeiss510 room and configured appropriately to meet the experimental conditions of the users. The University is supporting this proposal with $200,000 to purchase the requested system. In summary, the requested instrument will provide the research community at the University of Virginia and beyond with a level of imaging capability that is not currently available, and this will enhance significantly ongoing and future research.